Elastase is the only known proteolytic enzyme with the capability of degrading the protein elastin. This protein is responsible for much of the elasticity exhibited by lung tissue and since this elasticity is drastically reduced in the emphysematous state it is attractive to speculate that this change is due to the mediation of the enzyme elastase. These studies are designed around a homologous system using domestic swine as the experimental animal. The in vitro interaction of elastase (pancreatic, leucocyte) and the inhibitors from serum and lung will be thoroughly characterized prior to the induction of experimental emphysema by elastase. It is believed that a more clear understanding of the role of elastase in the pathogenesis of emphysema will be obtained.